This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the presently described embodiments. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present embodiments. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
The treatment of degenerative lumbar spinal stenosis is conventionally treated by wide laminectomy and decompression of the spinal canal with or without spinal fusion. Spinal fusion, when required because of destabilization from the decompression, is usually associated with internal fixation making it a major procedure with significant morbidity to the patient.
Degenerative lumbar spinal stenosis causes neurological symptoms in the lower extremities and/or back pain. The symptoms may be constant with variations in intensity, depending upon position and activity, or may be intermittent and brought on by certain activities, particularly walking and standing.
The positional nature of the symptoms may be due to instability but most often is due to the fact that the normal posture of the lumbar spine is one of lordosis, which decreases the cross-sectional area of the spine. When the patient is sitting, lordosis decreases, increasing the cross-sectional area and relieving the symptoms.
Interspinous mechanical blocking devices, such as X-Stop by Medtronic, are commercially available. Such devices are pushed through the interspinous ligament and work by blocking extension of the spine. Unfortunately, such device has a very high failure rate, largely because the spinous process is the weakest part of the vertebra, but also because the population demographics of people requiring this type of operation are such that many of them suffer from osteoporosis.
Recently, another device, Coflex® by Paradigm Spine, LLC, was commercially released in the United States. This device is inserted by resecting the interspinous ligament and some of the inferior edge of the superior spinous process at the level which the device is to be inserted. Flanges at each end of the device can be pressed down so that they grasp the spinous process above and below. The flanges also contain holes through which small screws can be inserted.
This device also has a relatively high failure rate. The device has a fairly large diameter curve to make insertion of the device easier. This design results in forces which contain a vector attempting to displace the device back outwards from its position in the spine. If no securing screws have been placed, the device tends to dislocate posteriorly, resulting in a return of symptoms. If one screw is used, the device tends to pivot around that screw as it dislocates posteriorly, resulting in the same return of symptoms due to failure to prevent increased lumbar lordosis. When two screws are used, particularly where there is osteoporosis in the spinous process, the spinous process may fracture through the screw hole(s), resulting in posterior displacement.
Accordingly, there is a need for a blocking device for alleviating back pain. There is a need for such a blocking device to be easily inserted with a smaller incision than with insertion of conventional devices. There is further a need for such a blocking device to remain in place. There is still further a need for such a blocking device to be capable of extraction. There is a still further a need for tooling for easily inserting and extracting such a blocking device.